Clarifier and method

ABSTRACT

A fluid, such as air or water, carrying suspended solids is directed between a pair of oppositely charged, corrugated surfaces in order to subject the flow to an undulating action that increases the frequency with which the solid particles impinge against one another, thereby increasing the rate of flocculation of the solids. In the case of airborne particles, the corrugated surfaces are arranged in an upright condition so that the flocculated particles attracted to one or the other of such surfaces gravitate therefrom into a conveying mechanism that delivers such particles to a collecting receptacle. In the case of liquid-borne particles, the flow is forced to travel upwardly against the force of gravity after passing between the surfaces, thereby encouraging the flocculated particles to settle out into a sump that is associated with the uphill flow passage. In each case, two sets of charged surfaces may be utilized, the first having at least one of its surfaces insulated from the flow for electrostatic action only, while the second has neither surfaces so insulated for electrolytic action.

This invention relates to a continuation in many respects of theprinciples set forth in my co-pending application, Ser. No. 713,251,filed Aug. 10, 1976, and titled "Suspended Solids Extraction System andMethod," and in other respects relates to alternatives to suchteachings.

While, as before, the best flocculation of suspended solids in a liquidor other fluid seems to result when the fluid is subjected first to anelectrostatic treater, and secondly to an electrolytic treater, evenwhen taken individually, the action obtained with each of said treatersmay in many instances be improved when the electrodes thereof arecorrugated rather severely so that the flow, when forced to travelthrough the undulating pathway defined by such corrugated surfaces, isundulated to such an extent that the suspended solids impinge againsteach other with greater frequency, thereby increasing the rate offlocculation. Moreover, I have developed a composite unit that combinesboth an electric treater and a clarifier in a single unit so that theeffluent leaving such unit contains a lower concentration of suspendedsolids than heretofore possible, thereby requiring less settling time inopen basins and the like downstream from such treaters.

Accordingly, one important object of the present invention is tocontinue many of the important principles of my prior invention as setforth in the aforesaid co-pending application, but at the same time toexpand upon and in many instances provide alternatives for suchprinciples.

Another important object of the present invention is to provide a way ofincreasing the frequency of collisions or impingement of solid particleswith one another during passage through a treating unit, electric orotherwise, such as to thereby increase the likelihood of forming flocfrom the suspended solids of sufficient size that it can be readilysettled out.

An additional important object of this invention is to embody means forachieving the foregoing object in structures that are designed primarilyfor liquid flow and structures designed primarily for gaseous flow.

Another important object of the invention is to provide a treating unitof composite design that combines both electric treating sections andclarifier or settling sections in a single unit, thereby providing for alower level of solid particulate matter in the effluent leaving thetreater than has heretofore been possible.

In the drawings:

FIG. 1 is a schematic view of a system employing the principles of thepresent invention;

FIG. 2 is an enlarged, fragmentary, vertical cross-sectional view of twomajor treating components of the system in FIG. 1;

FIG. 3 is an enlarged, fragmentary, vertical cross-sectional view of apair of corrugated treating surfaces in the electrostatic treating unitof the system;

FIG. 4 is a view similar to FIG. 3 of corrugated surfaces in theelectrolytic treating unit of the system;

FIG. 5 is an enlarged, cross-sectional view of the corrugated surfacesof the electrostatic unit taken along line 5--5 of FIG. 3;

FIG. 6 is an enlarged, vertical cross-sectional view of an alternativearrangement for the corrugated surfaces suitable for eitherelectrostatic or electrolytic use but illustrating by way of example theelectrostatic usage; and

FIG. 7 is a perspective view of a treater intended primarily for use inremoving airborne solids.

The reservoir 10 receives a body of liquid to be treated through aninlet 12 and discharges the liquid through an outlet 14, assisted inthis operation by a pump 16. The pump in turn delivers the liquid intoan electrostatic treater 18, from whence it is delivered to anelectrolytic treater 20 via a short conduit 22. The effluent ultimatelyleaving the electrolytic treater 20 through discharge line 24 may thenbe directed into a series of settling basins 26, 28 and 30 is sodesired, the nature and operation of such basins 26-30 being fully setforth in my co-pending application above referred to.

The two treaters 18 and 20 are of virtually identical construction, theonly exception being in the nature of their specific electrodeconstructions, and therefore the following description will be directedtoward the treater 18 only, with the understanding that the sameprinciples apply to the treater 20 and the latter's components will bedesignated by the same numeral as those of the treater 18 with theaddition of the letter designation "a."

Treater 18 has a pair of vertically stacked tanks 32 and 34, the lowertank 32 being adapted to encourage flocculation of solids that aresuspended in the treated fluid and the upper tank 34 being adapted topromote settling out of such flocculated solids and, thus, clarificationof the liquid. An inlet 36 is coupled in flow communication with thelower tank 32 via entryway 38, while such inlet 36 is isolated from theupper tank 34 by means of a transverse partition. The lower tank 32 isinclined downwardly away from the entryway 38 and inlet 36 so that thereis an inherent tendency for the liquid entering the tank 32 to flow fromleft to right through the latter (viewing FIG. 2) toward a connectingpassage 42 that joins the lower tank 32 with the upper tank 34. Passage42 is essentially vertically disposed and is defined partially by abaffle 44 disposed across the downstream end of the tank 32 such as toforce the liquid leaving the latter to abruptly change directions inorder to enter the passage 42. An inclined top wall 46 of the tank 32serves also as the inclined floor of the upper tank 44.

A sump 48 is located at the downstream end of the tank 32 in associationwith the passage 42 and the baffle 44 for the purpose of collectingflocculated particles that are unable to overcome the force of gravityand travel upwardly with the liquid flow into the upper tank 34. Ifdesired, although entirely optional, a second sump 50 may be provided atthe upstream end of the tank 32, although it is contemplated that suchsump 50 will not normally be required or of significant value inconjunction with the first treater 18, its usage becoming morebeneficial in connection with the second treater 20 wherein particleswill already have been subjected once to an electric action by the timethe sump is encountered. A nozzle 52 or the like situated immediatelyadjacent the downstream end of the tank 32 at the upper end of the sump48 may be used to inject air or other gaseous bubbles into the flow forthe purpose of agitating the liquid within the tank 32. Moreover, aswill become apparent below, as a result of the electric fieldestablished within the tank 32, the bubbles from nozzle 52 will becomecharged, providing an attractive "particle" against which the solidparticles may become attached, thereby augmenting the flocculatingaction. An additional nozzle 54 below the upstream end of the tank 32and at the head of the sump 50 may also be employed.

The upper tank 34 is in the nature of a clarifying or settling basin,and as such has a weir 56 rising above the floor 46 adjacent the outletconduit 22 for the purpose of maintaining a predetermined liquid levelwithin the tank 34. Once the fluid reaches the top of the weir 56, itcan flow over the latter into the outlet 58 that evolves into theconduit 22.

The treater 18 may be flushed periodically to remove accumulated sludgeby virtue of a flush tank 60, holding a supply of flushing liquid, thatis controlled by a suitable valve 62 associated with a flush line 64that communicates with the entryway 38 at the upstream end of the tank32. Valves 66 and 68 control discharge lines 70 and 72, respectively,from the sumps 48 and 50, such valves 66 and 68 being opened by theirrespective actuators 74 and 76 at such times to provide escape outletsfor the accumulated sludge and flushing medium.

As illustrated schematically in FIG. 2, but in more detail in FIGS. 3and 5, the tank 32 houses electric field generating structure in thenature of vertically spaced layers of electrodes. As illustrated in FIG.3, each adjacent pair of electrodes 78 and 80 are connected to oppositesides of a source of direct electrical potential for the purpose ofgenerating an electric field therebetween. At least one of suchelectrodes 78, 80 is insulated from the liquid that flows therebetween,in this instance both electrodes 78 and 80 being fully insulated. Oneexpeditious way of accomplishing such arrangement has been found bysandwiching a layer of conductive metal foil 82 between two dielectriclayers 84 and 86 as illustrated with respect to the positively chargedelectrode 78. As a result of such insulation, there is no current flowacross the space between the electrodes 78, 80.

Each of the electrodes 78, 80 is corrugated transversely of thedirection of fluid flow therethrough so as to present a pair of opposed,corrugated surfaces between which the liquid must flow in order to reachthe downstream end of the tank 32. In FIG. 3 the ridges 88 of theadjacent electrodes 78, 80 are aligned, as are their valleys 90, suchthat the flow path is of generally uniform width, although serpentine,from the upstream end to the downstream end of the tank 32.

In FIG. 6, however, showing an alternative electrode arrangement, itwill be seen that the ridges 188 of one electrode are aligned with thevalleys 190 of the other electrode, thereby producing alternating zonesof expansion and contraction to which the flowing liquid is successivelysubjected during its movement through the tank 32. Note further in thislatter arrangement that the lines of force between the opposedelectrodes 178 and 180 are concentrated at the points where the path isthe narrowest, as contrasted to the arrangement in FIG. 3 where thelines of force are substantially evenly dispersed throughout. In eitherarrangement, it is to be noted that the longitudinal axes of thecorrugations, defined by the ridges 88, 188 and the valleys 90, 190, asthe case may be, extend transversely of the flow path of the fluid.

The tank 32a of the electrolytic treater 20 differs from the tank 32 ofthe electrostatic treater 18 only with respect to the nature of itselectrodes. In the tank 32a, the electrodes 78a and 80a have nodielectric layers and are, thus, not electrically insulated from theflowing liquid. Consequently, electrolytic action occurs.

Operation of the Embodiments in FIGS. 1-6

When the liquid containing suspended solids enters the treater 18through the inlet 36, it is prevented from entering the top tank 34 bythe partition 40 and is directed instead through the entryway 38 at thehead of the tank 32. As it flows from left to right viewing FIG. 2through the tank 32, it is undulated rather dramatically by thetransversely corrugated surfaces presented by the electrodes 78, 80.Thus, in addition to the effect of the electric field on the liquidtending to flocculate the suspended solids, the undulating movementimparted to the liquid causes an increased rate of collision orimpingement between the solid particles, thereby augmenting the work ofthe electric field. Further augmenting this action is the presence ofnumerous gas bubbles from the nozzles 52 and 54 which become charged bythe presence of the electric field in the tank 32 to not only agitatethe liquid further, but to also provide adhering surfaces for theparticles.

Consequently, by the time the liquid reaches the downstream end of thetank 32, a sufficiently large amount of flocculation has occurred sothat some of the floc can be settled out. This is encouraged by thepresence of the baffle 44 and the upright nature of the connectingpassage 42 to the upper tank 34, this arrangement forcing the liquid toabruptly change directions and move upwardly against the force ofgravity such that flocculated particles will tend to settle down intothe sump 48.

Those particles which have not flocculated sufficiently to drop out ofthe liquid during its upward movement through passage 42 are carriedupwardly into the tank 34 where additional settling can occur. As aresult of the weir 56, the level within the tank 34 must reach apreselected height before fluid can depart through the outlet 58.Consequently, the liquid pools behind the weir 56 to promote settlingout of the solids, which in turn have a tendency to slide down theinclined floor 56 and drop through the passage 42 into the sump 48.

Normally, the desired amount of separation of the suspended solids fromthe liquid carrier cannot be obtained with the treater 18 alone, andthus the effluent from the treater 18 is directed through the conduit 22into the electrolytic treater 20 for a second treatment. The undulatingaction imposed upon the liquid by virtue of the corrugations within thetank 32a is the same as that obtained within the electrostatic tank 32,but in tank 32a the liquid is exposed to a more powerful electric actionin the nature of electrolysis. The flocculated particles leaving thetank 32a must once again overcome gravity to travel through the passage42a into the clarifying upper tank 34a such that, at this point, thefloc tends to settle into the sump 48a. Upon reaching the tank 34a,further settling and clarification occurs as a result of the weir 56acausing the liquid to pool sufficiently to induce the flocculatedparticles to settle onto the floor 46a and subsequently slide down thelatter into the sump 48a.

From the electrolytic treater 20, the clarified liquid may travelthrough the discharge line 24 into the final clarifying tanks 26, 28 and30, if desired, although it has been found in many instances that suchadditional clarification by the tanks 26-30 is not required. Sludge thataccumulates within the sumps 48 and 48a, as well as any that may haveaccumulated in the sumps 50 and 50a, may be periodically flushed byopening the valves 62, 62a; 66, 66a; and 68, 68a. Normally, it iscontemplated that the valves 68, 68a will remain closed until after thetanks 32, 32a have been flushed with the valves 66, 66a open, therebyassuring that the flushing medium does, in fact, flow properly throughthe tanks 32, 32a.

When the electrodes 78, 80 and 78a, 80a are arranged in the mannerillustrated in FIGS. 3 and 4, the flowing liquid is not exposed to asaggressive an action as that obtained with the electrode arrangementillustrated in FIG. 6. In the latter arrangement, the alternatingsqueezing and releasing action has in some instances been found to betoo violent; and in such instances, the gentler arrangement of FIGS. 3and 4 is to be preferred. Each case must be decided on its own merits,considering the nature of the influent and the resistance toflocculation of the solids suspended therein.

DUST COLLECTOR OF FIG. 7

The collector 92 operates in many respects like the treating arrangementof FIGS. 1-6 because gaseous-borne solids entering the inlet 94 aresubjected to transversely corrugated surfaces presented by the pack ofalternately charged electrodes, two of which are indicated by thenumerals 96 and 98, respectively. Preferably, the electrodes 96 and 98are of the insulated "sandwich" construction illustrated in FIG. 3 sothat no electrical current flows therebetween. The undulating actionimparted to the gas flow causes an increased frequency of collision ofthe solid particles, and the charged nature of the electrodes 96, 98provides attractive surfaces for the particles which may themselves beoppositely charged.

The electrodes 96, 98 are vertically disposed within the housing 100such that particles collecting thereon will inherently gravitate intothe conveyor mechanism 102 (illustrated in the nature of an auger 104),whereupon they can be drawn off into the collecting receptacle 106. Thegas itself may be exhausted from the collector 92 through the stack 108situated at the end of the housing 100 remote from the inlet 94.

In the case of the liquid treating system illustrated in FIGS. 1-6, suchan arrangement has been found to be particularly, although notexclusively, useful in connection with a dairy processing facilitywherein it is necessary to remove such suspended solids as whole milk,cream, butterfat, yogurt and even some fecal materials. The collector ofFIG. 7 has been found to be extremely helpful in connection with dryersthat are used to remove the moisture from sludge obtained by using thesystem of FIGS. 1-6, the dryers by virtue of a strong airflow tending toentrain minute solid particles from the sludge and discharge the sameinto the atmosphere unabated when the collector 92 is not used.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:
 1. In a method of removing suspendedsolids from a fluid, the improvement that includes the step of directingthe fluid to be treated between a pair of opposed, oppositelyelectrically charged, corrugated surfaces in a direction transverse tothe longitudinal axes of the corrugations so as to subject the fluid toan undulating action that encourages flocculation of the solids throughdirect impingement against one another, said surfaces being so arrangedthat peaks of the corrugations facing toward the fluid are disposeddirectly opposite one another so as to subject the fluid to alternatingforces of constriction and expansion along the flow path in conjunctionwith sequential exposure to concentrated electrical lines of force. 2.In a method as claimed in claim 1, wherein at least one of said surfacesis electrically insulated from the fluid.
 3. In a method as claimed inclaim 1, wherein neither of said surfaces is electrically insulated fromthe fluid.